WO2020161008A1

WO2020161008A1 - Lubricant composition for preventing pre-ignition

Info

Publication number: WO2020161008A1
Application number: PCT/EP2020/052397
Authority: WO
Inventors: Steve FAURE; Géraldine PAPIN
Original assignee: Total Marketing Services
Priority date: 2019-02-04
Filing date: 2020-01-31
Publication date: 2020-08-13
Also published as: FR3092335B1; CN113490732A; KR20210139243A; EP3921397A1; US20220119726A1; JP2022519614A; FR3092335A1

Abstract

The present invention relates to the use of a lubricant composition comprising (i) at least one boron derivative; and (ii) at least one base oil, for preventing and/or reducing pre-ignition, in particular at low speed, in a vehicle engine, wherein said composition is used during at least one change interval without the addition of a new lubricant composition, the content of boron in the composition being between 150 ppm and 350 ppm by weight.

Description

LUBRICANT COMPOSITION TO PREVENT PRE-IGNITION

Technical area

The present invention relates to the field of lubricants, in particular usable in vehicle engines, in particular lubricating compositions making it possible to prevent or reduce pre-ignition in an engine.

Under ideal conditions, normal combustion in a spark-ignition engine occurs when a mixture of fuel, especially fuel and air is ignited in the combustion chamber inside the cylinder by the production of a spark from a spark plug. Such normal combustion is generally characterized by the expansion of the flame front through the combustion chamber in an orderly and controlled manner.

However, in some cases, the air / fuel mixture can be prematurely ignited by an ignition source before ignition by the spark from the spark plug, leading to a phenomenon known as pre-ignition.

However, it is preferable to reduce, or even eliminate, the pre-ignition because this generally results in the presence of a strong increase in temperatures and pressures in the combustion chamber, and thus have a significant negative impact on the combustion chamber. efficiency and overall performance of an engine. Additionally, pre-ignition can cause significant damage to the cylinders, pistons, spark plugs and valves in the engine and in some cases can even result in engine failure or even engine breakage.

More recently, low speed pre-ignition (Low Speed Pre-Ignition in English or "LSPI") has been identified, in particular by car manufacturers, as a potential problem for small, so-called "downsized" engines. LSPI typically occurs at low speeds and high loads, and can cause severe damage to pistons and / or cylinders.

In addition, the prevention and / or reduction of pre-ignition, in particular of LSPI, must be maintained over time, that is to say during prolonged use of the lubricating composition, for example between two oil changes or after a certain number of kilometers traveled. Prior art

Several theories have been put forward in an attempt to explain this complex phenomenon. In particular, it has been observed that the presence of small amounts of lubricant in the combustion chamber coming to mix with the fuel can worsen pre-ignition. Also, a link between the presence of deposit in the combustion chamber and the occurrence of LSPI phenomena has been established. Finally, the design of the engine itself can influence pre-ignition.

Thus, this phenomenon is very complex and difficult to predict. As specified above, the nature of the lubricant contributes strongly to this and lubricating compositions making it possible to prevent or reduce the risk of pre-ignition, in particular LSPI, have therefore already been proposed.

Thus, application WO 2015/023559 describes a method for reducing pre-ignition by adding, in a lubricating composition, an additive making it possible to delay ignition, said additive being chosen from organic compounds comprising at least one aromatic nucleus.

However, these light organic compounds could cause an excessive increase in lubricant volatility.

It has therefore also been proposed to add polyalkylene glycol, as described in application WO 2017/021521, or else to integrate an organomolybdenum compound chosen from molybdenum dithiophosphates and sulfur-free molybdenum complexes, according to document WO 2017/021523, in a lubricating composition in order to prevent or reduce pre-ignition in an engine.

It is also known that the content of calcium-based detergent is a strong lever for triggering LSPI. Thus, it has been suggested to substitute detergents based on calcium with detergents based on magnesium in lubricating compositions intended to reduce LSPI in vehicle engines.

The inventors have been able to observe that the phenomenon of pre-ignition intensifies during the prolonged use of the lubricating composition. Thus, pre-ignition is particularly exacerbated in the case of so-called “used” lubricating compositions. In particular, it has already been demonstrated that lubricating compositions exhibiting a reduction in LSPI phenomena when they are new, see their properties deteriorate when they are used, in particular in the document “Low-speed pre-ignition”, Engine technology international, September 2018.

Finally, the solutions recommended in the prior art for new lubricating compositions prove insufficient in the case of used compositions.

Document US 2015/322367 A1 describes a method for preventing or reducing LSPI in an engine lubricated with a composition comprising a base oil and a detergent comprising an alkaline earth metal of an organic acid.

However, this document makes no mention of the specific properties that may be conferred by a boron derivative on the lubricating composition comprising it, nor of the presence of a specific boron content.

Furthermore, the combination of at least one molybdenum derivative, and at least one boron derivative has already been described in application WO 2017/013238 for the purpose of retaining the fuel economy properties of a lubricating composition.

However, this document in no way suggests a possible effect of this combination, or of any of the additives taken in isolation, on the pre-ignition phenomena that may occur in the engine.

For the purposes of the present invention, the term “used lubricating composition” is intended to denote a lubricating composition used during at least one oil change interval, that is to say over a distance traveled by the vehicle of between 10 000 and 30,000 km, preferably between 15,000 and 30,000 km.

The expressions "in the long term" or "in the long term" used according to the invention mean that the application of the lubricant composition extends to a used lubricant composition.

For the purposes of the present invention, the term “new lubricating composition” is intended to denote a lubricating composition that has never been used in an engine. For the purposes of the present invention, the term “aged lubricating composition” is intended to denote a lubricating composition which has undergone artificial aging, by simulation of the conditions of use of the lubricating composition in an engine. This artificial aging makes it possible to reproduce in an accelerated manner the aging of the oil when it is used in an engine during an oil change interval. In particular, it is a lubricating composition which has undergone an iron-catalyzed oxidation at a temperature above 150 ° C, preferably between 150 ° C and 170 ° C and for a period of at least 10 h, preferably between 120 h and 150 h, according to the GFC Lu-43 Al 1 method.

All of the embodiments defined according to the present invention for a used lubricating composition are applicable to an aged lubricating composition.

As stated above, pre-ignition phenomena tend to worsen during the implementation of a lubricating composition which is therefore only really effective when it is new. For obvious reasons, it is necessary to offer a solution for preventing pre-ignition that is sustainable over time,

There therefore remains a need for lubricating compositions having the capacity to prevent and / or reduce the pre-ignition, in particular LSPI, of an engine, in particular of a motor vehicle engine, for a prolonged period of time. of its use, more precisely when the lubricating composition is used.

The solutions favored in the prior art recommend selecting particular additives, making it possible to play a role in reducing the pre-ignition phenomena taking place within the engine. However, the lubricating compositions can integrate a large number of different additives, allowing them to be given particularly advantageous properties, without it being possible to predict which additives will have a beneficial impact on the prevention of pre-ignition, a fortiori on the long term.

There therefore remains a need to provide additives which make it possible, once implemented in a lubricating composition, to prevent and / or reduce the pre-ignition phenomena which may occur during its prolonged use in an engine. Finally, it is necessary to provide a pre-ignition prevention solution that does not require the addition of new lubricating composition to the engine during its prolonged use, in particular between the engine oil change intervals.

Thus, there still remains a need to provide a lubricating composition making it possible to prevent and / or reduce pre-ignition during its implementation in an engine, not requiring the addition of lubricating composition between each engine oil change interval. .

Furthermore, during their prolonged use in engines, lubricating compositions tend to oxidize. This can result in a change in viscosity of the composition, the presence in the composition of oxidation residues or the formation of deposits on parts in contact with the composition. These phenomena are likely to negatively impact all of the properties, in particular use, of the lubricating composition, and thus reduce its life and / or the oil change interval.

There therefore also remains a need to provide lubricating compositions which are resistant to oxidation, in particular which are less impacted by the harmful phenomena linked to oxidation, during their prolonged use, in particular between the engine oil change intervals. .

The present invention is aimed precisely at meeting these needs.

Summary of the invention

Thus, the present invention relates, according to a first of its aspects, to the use of a lubricating composition comprising

(i) at least one boron derivative;

(ii) at least one base oil,

to prevent and / or reduce pre-ignition, in particular at low speed, in a vehicle engine, preferably a motor vehicle,

said composition being used during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without adding new lubricating composition,

the boron content present in the composition being between 150 ppm and 350 ppm by weight. The term “motor vehicle” within the meaning of the present invention is understood to denote a vehicle comprising at least one wheel, preferably at least two wheels, propelled by an engine, in particular a combustion and explosion engine, in particular an internal combustion engine. reciprocating or rotary pistons, Diesel or spark ignition. Such engines can for example be four-stroke or two-stroke gasoline or diesel engines.

According to the invention, the prevention and / or reduction of pre-ignition is preferably measured for the used lubricating composition relative to the new lubricating composition.

Against all expectations, and as emerges from the examples appearing below, the inventors have demonstrated that the addition of at least one boron derivative in an aged lubricating composition makes it possible to significantly improve the ignition temperature of said composition and consequently to delay the pre-ignition phenomena, in particular LSPI, liable to occur during its implementation in an engine. The ignition temperature here refers to the initiation temperature of the exothermic peak during a rise in temperature, measured by high pressure differential scanning calorimetry known as "HPDSC" (High Pressure Differential Scanning Calorimetry).

The boron derivatives present in a lubricating composition according to the invention therefore advantageously make it possible to prevent pre-ignition phenomena, in particular LSPI, during its use during at least one drain interval, preferably over a distance traveled by the vehicle between 10,000 km and 30,000 km.

In addition, as the examples below demonstrate, a boron content in the lubricant composition of at least 150 ppm by weight is required to obtain an advantageous effect on the prevention of pre-ignition phenomena, in particular especially from LSPI.

Furthermore, the inventors have also demonstrated that the addition of at least one boron derivative in a new lubricating composition, with a boron content in the composition of less than or equal to 350 ppm by weight, advantageously makes it possible to maintain resistance to the satisfactory oxidation of said composition. A lubricating composition used according to the invention therefore advantageously exhibits limited oxidation during its prolonged use in an engine, in particular during an oil change interval.

As a result, it is not necessary to renew the lubricating composition during its use, for example between two engine oil changes, in order to keep prevention and / or reduction of pre-ignition phenomena, in particular at low speed, effective. .

Another subject of the invention, according to another of its aspects, is the use of at least one boron derivative, in particular as defined below, in a lubricating composition comprising at least one base oil, the content boron present in the composition being between 150 ppm and 350 ppm by weight, to prevent and / or reduce pre-ignition, in particular at low speed, in a vehicle engine, preferably a motor vehicle, said lubricating composition being implemented during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without adding new lubricant composition.

Another subject of the invention, according to another of its aspects, is the use of at least one boron derivative, in particular as defined below, in a lubricating composition comprising at least one base oil, the content boron present in the composition being between 150 ppm and 350 ppm by weight, to limit the degradation of the performance of prevention and / or reduction of pre-ignition, in particular at low speed, in a vehicle engine, preferably of motor vehicle, of said composition, after its implementation during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without addition of new lubricating composition.

A further subject of the invention is a method for preventing and / or reducing pre-ignition, in particular at low speed, in a vehicle engine, preferably of a motor vehicle, preferably in the long term, comprising at least the following steps: a) bringing the engine into contact with a lubricating composition comprising at least one base oil and at least one boron derivative, the boron content present in the composition being between 150 ppm and 350 ppm by weight;

b) operation of the engine during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without adding new lubricant composition.

The invention also relates to the use of a lubricating composition comprising:

(i) at least one boron derivative; and

(ii) at least one base oil,

said composition having undergone an iron-catalyzed oxidation at a temperature above 150 ° C, preferably between 150 ° C and 170 ° C and for a period of at least 110 h, preferably between 120 h and 150 h, according to the GFC Lu-43A-11 method, the boron content present in the composition being between 150 ppm and 350 ppm by weight.

detailed description

COMPOSITION

Boron derivative

As mentioned above, a lubricating composition used according to the present invention comprises (i) at least one boron derivative.

The boron derivative can in particular be chosen from boric acid derivatives, boronic acid derivatives, boronates, borates, borated dispersants, such as succinimide boron derivatives, in particular borated polyisobutene succinimide, borate detergents, such as borate carboxylates, simple orthoborates, borate epoxides, borate esters, and mixtures thereof.

More preferably, the boron derivative can in particular be chosen from esters of C10-C24 fatty acids of borate, borated dispersants, such as boron succinimides derivatives, in particular borated polyisobutene succinimide and their mixtures. The boron derivatives which can be used according to the present invention are compounds which are well known to those skilled in the art and can be obtained by any process also known to those skilled in the art.

Boron derivatives are known more particularly for their use in a lubricating composition in order to maintain a good level of fuel economy in an engine.

These compounds are also known for their use as a dispersing or detergent agent in lubricating compositions.

As an example of a commercial boron derivative can be cited the borate ester Oloa® 17503 from Oronite.

The boron content present in a lubricating composition used according to the invention is between 150 ppm and 350 ppm by weight.

The boron derivative can be present in a lubricating composition used according to the invention in a content ranging from 0.01% to 3% by weight, preferably from 0.05% to 2.5% by weight, more preferably from 0 , 1% to 2% by weight, relative to the total weight of the composition, as long as the total boron content in the lubricating composition is between 150 ppm and 350 ppm by weight.

According to one embodiment, the lubricating composition used according to the invention comprises from 150 to 300 ppm by weight of boron, preferably from 160 to 260 ppm by weight of boron.

Base oil

As specified above, a lubricating composition used according to the present invention comprises (ii) at least one base oil.

The base oil (s) can be oils of mineral, synthetic or natural, animal or plant origin, known to those skilled in the art.

In particular, the mineral or synthetic oils generally used in the lubricating composition belong to one of groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) as summarized in Table 1 below. below. The API classification is defined in American Petroleum Institute 1509 "Engine oil Licensing and Certification System" 17th edition, September 2012.

The ATIEL classification is defined in "The ATIEL Code of Practice", issue 18, November 2012.

TABLE 1

There is generally no limitation as to the use of oils of different bases to produce a lubricating composition used according to the invention, except that they must have properties, in particular of viscosity, of viscosity, sulfur content, oxidation resistance, suitable for use in engines, especially vehicle engines.

Mineral base oils include all types of bases obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, deasphalting, solvent dewaxing, hydrotreatment, hydrocracking and hydroisomerization, hydrofinishing.

The synthetic base oils can be chosen from esters, silicones, glycols, polybutene, polyalphaolefins (PAO), alkylbenzene or alkylnaphthalene.

The base oils can also be oils of natural origin, for example esters of alcohols and carboxylic acids, obtainable from natural resources such as sunflower oil, rapeseed oil, palm oil, soybeans etc.

The base oil can be more particularly chosen from synthetic oils, mineral oils and their mixtures. According to one embodiment, a lubricating composition used according to the present invention comprises at least one base oil chosen from group III oils, group IV oils and their mixtures.

Additives

A composition used according to the present invention may further comprise one or more additives as defined more precisely in the remainder of the text, distinct from the boron derivative defined above.

The additives which can be incorporated into a composition according to the invention can be chosen from antioxidants, detergents distinct from the boron derivative defined above, viscosity index improvers, friction modifiers, anti-wear additives , extreme pressure additives, dispersants other than the boron derivative defined above, pour point improvers, antifoams and mixtures thereof.

It is understood that the nature and the amount of additives used are chosen so as not to affect the properties of the lubricating composition, in particular with regard to the prevention and / or reduction of pre-ignition, in particular of LSPI, in a motor.

These additives can be introduced singly and / or in the form of a mixture like those already available for sale for commercial lubricant formulations for vehicle engines, with a performance level as defined by the ACEA ( Association of European Automobile Manufacturers) and / or API (American Petroleum Institute), well known to those skilled in the art.

According to a particular embodiment, a composition used according to the invention may further comprise at least one antioxidant additive.

The antioxidant additive generally helps to delay the degradation of the composition in service. This degradation can be reflected in particular by the formation of deposits, by the presence of sludge or by an increase in the viscosity of the composition. Antioxidant additives act in particular as radical inhibitors or destroyers of hydroperoxides.

Among the antioxidant additives commonly used, mention may be made of antioxidant additives of phenolic type, antioxidant additives of amine type, phosphosulfurized antioxidant additives. Some of these antioxidant additives, for example additives phosphosulfurized antioxidants, can generate ash. The phenolic antioxidant additives can be free from ash or be in the form of neutral or basic metal salts.

The antioxidant additives can in particular be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted with at least one C1-C12 alkyl group, N, N '- Dialkyl-aryl-diamines and mixtures thereof.

Preferably according to the invention, the sterically hindered phenols are chosen from compounds comprising a phenol group of which at least one carbon vicinal of the carbon carrying the alcohol function is substituted by at least one C 1 -Cio alkyl group, preferably an alkyl group. C _I -C _O, preferably a C4 alkyl group, preferably tert-butyl group.

Amino compounds are another class of antioxidant additives that can be used, possibly in combination with phenolic antioxidant additives.

Examples of amino compounds are aromatic amines, for example aromatic amines of formula NR ⁴ R ⁵ R ⁶ in which R ⁴ represents an aliphatic group or an aromatic group, optionally substituted, R ⁵ represents an aromatic group, optionally substituted, R ⁶ represents a hydrogen atom, an alkyl group, an aryl group or a group of formula R ⁷ S (0) _z R ⁸ in which R ⁷ represents an alkylene group or an alkenylene group, R ⁸ represents an alkyl group, a alkenyl group or an aryl group and z represents 0, 1 or 2.

Sulfurized alkyl phenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives.

Another class of antioxidant additives is that of copper compounds, for example copper thio- or dithio-phosphates, copper and carboxylic acid salts, dithiocarbamates, sulfonates, phenates, copper acetylacetonates. Copper I and II salts, succinic acid or anhydride salts can also be used.

A composition used according to the invention can contain all types of antioxidant additives known to those skilled in the art. Advantageously, a composition used according to the invention comprises at least one antioxidant additive chosen from diphenylamine, phenols, phenol esters and their mixtures.

A composition used according to the invention can comprise from 0.05% to 2% by weight, preferably from 0.5% to 1% by weight, of at least one antioxidant additive, relative to the total weight of the composition.

According to another embodiment, a composition used according to the invention may further comprise at least one detergent additive distinct from the boron derivative required according to the present invention.

Detergent additives generally reduce the formation of deposits on the surface of metal parts by dissolving by-products of oxidation and combustion.

The detergent additives which can be used in a composition used according to the invention are generally known to those skilled in the art. The detergent additives can be anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head. The associated cation can be a metal cation of an alkali or alkaline earth metal.

The detergent additives are preferably chosen from alkali metal or alkaline earth metal salts of carboxylic acids, sulphonates, salicylates, naphthenates, as well as salts of phenates. The alkali metals and alkaline earth metals are preferably calcium, magnesium, sodium or barium.

These metal salts generally include the metal in a stoichiometric amount or else in excess, therefore in an amount greater than the stoichiometric amount. These are then overbased detergent additives; the excess metal providing the overbased character to the detergent additive is then generally in the form of a metal salt insoluble in oil, for example a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferably a carbonate .

A composition used according to the invention can contain all types of detergent additives known to those skilled in the art. Advantageously, a composition used according to the invention comprises at least one detergent additive chosen from alkaline earth metal salts, preferably from calcium salts, magnesium salts and mixtures thereof.

In particular, when the detergent is chosen from alkaline earth metal salts, the detergent additive can be added to the composition so as to provide a metal element content ranging from 150 ppm to 2000 ppm, preferably from 250 ppm to 1500 ppm.

According to yet another embodiment, a composition used according to the present invention may further comprise an additive improving the viscosity index.

As examples of additives improving the viscosity index, mention may be made of polymer esters, homopolymers or copolymers, hydrogenated or non-hydrogenated, of styrene, butadiene and isoprene, polyacrylates, polymethacrylates (PMA). or else olefin copolymers, in particular ethylene / propylene copolymers.

Advantageously, a composition used according to the invention comprises at least one additive improving the viscosity index chosen from homopolymers or copolymers, hydrogenated or non-hydrogenated, of styrene, butadiene and isoprene. Preferably it is a hydrogenated styrene / isoprene copolymer.

A composition used according to the invention may for example comprise from 2% to 15% by weight of additive improving the viscosity index, relative to the total weight of the composition.

Antiwear additives and extreme pressure additives protect rubbing surfaces by forming a protective film adsorbed on these surfaces.

There is a wide variety of antiwear additives. Preferably for the lubricating composition according to the invention, the anti-wear additives are chosen from phospho-sulfur additives such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates or ZnDTP. The preferred compounds are of formula Zn ((SP (S) (OR ² ) (OR ³ )) 2, in which R ² and R ³ , identical or different, independently represent an alkyl group, preferably an alkyl group comprising from 1 to 18 carbon atoms.

Amine phosphates are also antiwear additives which can be used in a composition according to the invention. However, the phosphorus provided by these additives can act as a poison in automotive catalytic systems because these additives generate ash. These effects can be minimized by partially substituting the amine phosphates with additives which do not provide phosphorus, such as, for example, polysulfides, in particular sulfur-containing olefins.

A composition used according to the invention can comprise from 0.01 to 6% by weight, preferably from 0.05 to 4% by weight, more preferably from 0.1 to 2% of antiwear additives and extreme additives. -pressure, by weight relative to the total weight of the composition.

A composition used according to the invention is preferably free from antiwear additives and extreme pressure additives. In particular, a composition used according to the invention can be free from phosphate additives.

A composition used according to the invention may comprise at least one friction modifier additive. The friction modifier additive can be chosen from a compound providing metallic elements and an ash-free compound. Among the compounds providing metallic elements, mention may be made of transition metal complexes such as Mo, Sb, Sn, Fe, Cu, Zn, the ligands of which may be hydrocarbon compounds comprising oxygen, nitrogen or carbon atoms. sulfur or phosphorus. The ash-free friction modifying additives are generally of organic origin and can be chosen from monoesters of fatty acids and polyols, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, fatty amines or glycerol esters. fatty acid. According to the invention, the fatty compounds comprise at least one hydrocarbon group comprising from 10 to 24 carbon atoms.

A composition used according to the invention can comprise from 0.01 to 2% by weight or from 0.01 to 5% by weight, preferably from 0.1 to 1.5% by weight or from 0.1 to 2% by weight. weight of friction modifier additive, relative to the total weight of the composition.

Advantageously, a composition used according to the invention is free of friction modifying additive.

A composition used according to the invention can also comprise at least one pour point reducing additive. By slowing the formation of paraffin crystals, pour point depressant additives generally improve the cold behavior of the composition.

Examples of pour point depressant additives include polymethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, alkylated polystyrenes.

Also, a composition used according to the invention may comprise at least one dispersing agent, distinct from the boron derivative required according to the present invention.

The dispersing agent can be chosen from Mannich bases, succinimides and their derivatives.

A composition used according to the invention may for example comprise from 0.2 to 10% by weight of dispersing agent distinct from the boron derivative required according to the present invention, relative to the total weight of the composition.

APPLICATIONS

A lubricating composition according to the invention is intended more particularly to be used in an engine, in particular in a vehicle engine, in particular in a gasoline vehicle engine.

It therefore advantageously exhibits properties, in particular viscosity, viscosity index, sulfur content, resistance to oxidation, suitable for use in engines, in particular vehicle engines.

Thus, preferably, a lubricating composition has a kinematic viscosity measured at 100 ° C according to the ISO 3104 standard of between 5 and 20 mm ² / s, preferably between 5 and 15 mm ² / s and more particularly between 6 and 13 mm ² / s.

As indicated above, a composition as described above is advantageous in that it makes it possible, by its implementation in an engine, to prevent and / or reduce the pre-ignition phenomena occurring within said engine over the long term. term, in particular after use for a period corresponding to at least one oil change interval. Thus, the invention relates to the use of a composition as defined above for preventing and / or reducing pre-ignition, in particular at low speed, in a vehicle engine, preferably of a motor vehicle, said composition being used. implemented during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without adding new lubricant composition.

In particular, the pre-ignition phenomena have been observed at low speed in engines (LSPI) and are more exacerbated in direct injection engines, in particular downsized.

Thus, the present application also relates to the use of a lubricating composition comprising:

(i) at least one boron derivative; and

(ii) at least one base oil,

for preventing and / or reducing low speed pre-ignition (LSPI) in a vehicle engine, preferably a motor vehicle, said composition being used during at least one oil change interval, preferably over a distance traveled by the vehicle between 10,000 km and 30,000 km, without adding new lubricant composition,

the boron content in the composition being between 150 ppm and 350 ppm by weight.

Particularly surprisingly, the inventors have found that the presence of a boron derivative in an aged lubricating composition makes it possible to significantly reduce the occurrence of pre-ignition phenomena in an engine.

Thus, the present invention also relates to the use of at least one boron derivative, in particular as defined above, in a lubricating composition comprising at least one base oil, the boron content in the composition being between 150 ppm and 350 ppm by weight, said lubricating composition being used during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without addition of lubricating composition new, for preventing and / or reducing pre-ignition, in particular at low speed, in a vehicle engine, preferably a motor vehicle.

As demonstrated in the examples below, the selection of a particular additive, namely a boron derivative, made it possible to propose a lubricating composition making it possible to prevent and / or reduce the pre-ignition phenomena which may occur during its prolonged use in an engine, without adding new lubricating composition.

Thus, still as demonstrated in the examples, a lubricating composition according to the invention has an ignition temperature higher than that obtained for a lubricating composition comprising no boron derivative or comprising an additional additive, distinct from the boron derivative required according to l 'invention.

In other words, the nature of the boron derivative was not clearly deductible from its possibly previously known functions.

The composition defined above therefore has the advantage of preventing and / or reducing pre-ignition in an engine, due to its prolonged use in an engine.

Thus, the invention also relates to a method for preventing and / or reducing pre-ignition, in particular at low speed, in a vehicle engine, preferably of a motor vehicle, preferably in the long term, comprising at least the following steps a) bringing the engine into contact with a lubricating composition comprising at least one base oil and at least one boron derivative, the boron content in the composition being between 150 ppm and 350 ppm by weight;

As specified above, a used lubricating composition used according to the invention has an ignition temperature higher than that of a used lubricating composition not in accordance with this definition. The ignition temperature here denotes the initiation temperature of the exothermic reaction measured by differential calorimetry high pressure scanning (HPDSC for "high pressure differential calorimetry" in English).

In particular, the temperature increase is at least 2%, preferably at least 4%, more preferably at least 5%, measured according to the protocol detailed in the examples, relative to the temperature of ignition of a lubricating composition comprising a base oil but being free from boron derivative.

Thus, the invention also relates to the use of at least one boron derivative, in particular as defined above, in order to increase the ignition temperature, measured by high pressure differential scanning calorimetry, of a lubricating composition, in particular of at least 2%, preferably at least 4%, said composition being used during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without the addition of new lubricating composition, relative to a used lubricating composition free of any compound derived from boron, the boron content in the composition being between 150 ppm and 350 ppm by weight.

According to the invention, the particular, advantageous or preferred characteristics of the composition according to the invention make it possible to define uses according to the invention which are also particular, advantageous or preferred.

Throughout the description, including the claims, the expression "comprising a" should be understood as being synonymous with "comprising at least one", unless specified to the contrary.

The expressions "between ... and ...", "includes from ... to ...", "formed from ... to ...", and "ranging from ... to ..." , must be understood with limits included, unless otherwise specified.

In the description and the examples, unless otherwise indicated, the percentages are weight percentages. The percentages are therefore expressed by weight relative to the total weight of the composition. Temperature is expressed in degrees Celsius unless otherwise specified, and pressure is atmospheric pressure, unless otherwise specified.

The invention will now be described by means of the following examples, given of course by way of illustration and without limitation of the invention. Examples

Methods

Lubricating Oil Aging Method

The oils used in the examples below were subjected to aging simulation. This simulation is performed by oxidation of oil catalyzed by 100 ppm iron at 170 ° C for 144 hours, according to the GFC-Lu-43A-11 method.

Laboratory measurement of the pre-ignition tendency

In the examples detailed below, the tendency to pre-ignition is determined in terms of the initiation temperature of the exothermic reaction, measured by high pressure differential calorimetric analysis, known as “HPDSC” (High Pressure Differential Scanning Calorimetry in English language).

This measurement is carried out on a Mettler Toledo LG3300 device according to the protocol detailed below:

- Weigh 2 ± 0.05 mg of sample to be analyzed in a cuvette;

- Place the open sample and the reference on the detector surface;

- The cell is closed hermetically and mechanically;

- A pressure between 1 and 20 bar is applied to the cell;

- The temperature of the sample is equilibrated at the starting temperature of the measurement, between 20 ° C and 80 ° C, preferably between 30 ° C and 70 ° C, maintained for 1 to 15 minutes, preferably for 2 at 10 minutes;

- At least one temperature ramp is applied to the sample, between the starting temperature and a temperature between 100 ° C and 400 ° C, preferably between 150 ° C and 350 ° C, more preferably between 200 ° C and 300 ° C.

Software, such as STARe software, can be used to visualize the differences in heat exchange between the sample and the reference.

The temperature of appearance of an exotherm on the curve thus obtained is assimilated to the phenomenon of pre-ignition, such as LSPI.

This temperature is correlated with time. Thus, the higher it is, the more the pre-ignition will be delayed in the combustion chamber during the implementation of the composition.

Oxidation measurement The resistance to oxidation of the lubricating compositions can be evaluated during aging with iron carried out according to the protocol (Method for aging lubricating oils) described above.

During the aging of the lubricating composition, samples of 20 ml of composition are taken at 72 hours, 96 hours and at 120 hours. A final sample of 125 mL is taken at the end of the 144 hours.

Each sample is characterized by its viscosity fluctuation (RKV100) by comparing the kinematic viscosity value measured at 100 ° C according to the ISO 3104 or ASTM D445 method at the time of sampling (KVlOOi) compared to its initial value before aging (KVlOOo) . The calculation carried out is as follows:,. _L

relative)

A value of RKV100 close to 0 means that the viscosity of the composition varies little between each sample, which demonstrates a weak oxidation.

Example 1: Preparation of lubricating compositions

The lubricating compositions AO to A3 were prepared.

Their kinematic viscosity at 100 ° C. was determined according to the ISO 3104 standard and their properties of predisposition to self-ignition were measured.

The details of the compositions are presented in Table 2 below, in which the proportions of different compounds are indicated in percentage by mass.

TABLE 2

* The additive pack is a mixture of various additives common in the field of lubricants and available commercially. It includes zinc dithiophosphate type antiwear agents, calcium and magnesium based detergents and PIB SI type dispersants.

In each of the compositions thus prepared, the amount of calcium is 1350 ppm by weight and the amount of magnesium is 300 ppm by weight.

(1) the amount of boron in the Al composition is 160 ppm by weight.

(2) the amount of boron in composition A2 is 260 ppm by weight.

(3) the amount of boron in composition A3 is 180 ppm by weight.

The compositions are prepared by mixing, at a temperature of the order of 30 to 40 ° C, the compounds detailed in Table 2.

The lubricating compositions thus prepared exhibit kinematic viscosity values at 100 ° C. suitable for their use in engines, in particular vehicle engines.

The lubricating compositions are then aged according to the protocol (aging method) detailed above.

Example 2: Evaluation of the LSPI performances of lubricating compositions

The initiation temperature of the exothermic reaction (ignition temperature) was measured for the reference oil and the lubricating compositions of Example 1, according to the measurement method (laboratory method of the tendency to pre- ignition) defined above.

The results are shown in Table 3 below.

TABLE 3

Compositions A1 to A3 according to the invention, comprising at least one boron derivative, exhibit higher ignition temperatures than for the same composition not comprising any boron derivative required according to the invention (reference composition A).

These measurements therefore make it possible to demonstrate that the addition of at least one boron derivative in an aged lubricating composition makes it possible to significantly delay the pre-ignition phenomena, in particular of LSPI, during its use in an engine, under conditions simulating the aging of the lubricating composition. In the examples which follow, the lubricating compositions are produced and tested in comparison with a reference lubricating composition, not comprising any boron derivative.

For this reference composition, the kinematic viscosity at 100 ° C was determined according to the ISO 3104 standard. The composition was then aged according to the catalyzed aging protocol described above, while performing measurements of the oxidation during aging, in accordance with the protocol detailed above. Finally, the initiation temperature of the exothermic reaction (ignition temperature) was measured, according to the measurement method (laboratory method of the tendency to pre-ignition) defined above.

The detail of the reference composition (in percentage by mass) and the results obtained are presented in Table 4 below.

TABLE 4

* The additive pack is a mixture of various additives common in the field of lubricants and available commercially. It includes zinc dithiophosphate antiwear agents, calcium and magnesium based detergents and PIB SI type dispersants.

Example 3: Preparation of lubricating compositions

The lubricating compositions B0 to B2 were prepared.

Their kinematic viscosity at 100 ° C. was determined according to the ISO 3104 standard. The details of the compositions are presented in Table 5 below, in which the proportions of different compounds are indicated in percentage by mass.

TABLE 5

(1) the amount of boron in the composition B0 is 180 ppm by weight.

(2) the amount of boron in composition B 1 is 45 ppm by weight.

(3) the amount of boron in composition B2 is 450 ppm by weight. The compositions are prepared by mixing at a temperature of the order of

30 to 40 ° C, compounds detailed in Table 5. The lubricating compositions thus prepared exhibit kinematic viscosity values at 100 ° C. suitable for their use in engines, in particular vehicle engines.

Example 4: Evaluation of the performances of the lubricating compositions The initiation temperature of the exotherm reaction (ignition temperature) was measured for the lubricating compositions of Example 1, according to the measurement method (laboratory method of the trend pre-ignition) defined above.

In addition, the oxidation of each of the lubricating compositions was also evaluated by measuring the fluctuation of the kinematic viscosity measured at 100 ° C (RKV100) throughout the aging of the compositions and in accordance with the protocol (Measurement of oxidation) described above.

The results are shown in Table 6 below.

The composition B0 according to the invention, comprising at least one boron derivative in a content of between 150 ppm and 350 ppm by weight, has both a ignition temperature higher than that measured for the reference composition and a very satisfactory resistance to oxidation.

On the other hand, composition B1, comprising less than 150 ppm by weight of boron exhibits a lower ignition temperature, which does not allow the desired level to be reached.

Regarding composition B2, although it has a higher ignition temperature, its stability to oxidation is very insufficient for use in an engine over the long term.

These measurements therefore make it possible to demonstrate that the addition of at least one boron derivative in an aged lubricating composition, providing the composition with between 150 ppm and 350 ppm by weight of boron, makes it possible to significantly delay the pre-ignition phenomena, in particularly of LSPI, during its use in an engine, under conditions simulating the aging of the lubricating composition, while exhibiting good resistance to oxidation.

Claims

1. Use of a lubricating composition comprising

(i) at least one boron derivative; and

(ii) at least one base oil,

2. Use according to claim 1, in which the boron derivative is chosen from boric acid derivatives, boronic acid derivatives, boronates, borates, borated dispersants, such as succinimide derivatives of boron. , in particular borated polyisobutene succinimide, borate detergents, simple orthoborates, borate epoxides, borate esters and mixtures thereof.

3. Use according to any one of claims 1 or 2, wherein the boron content varies from 150 to 300 ppm by weight, preferably from 150 to 260 ppm by weight.

4. Use according to any one of the preceding claims, in which the base oil is chosen from group III oils, group IV oils and mixtures thereof.

5. Use according to any one of the preceding claims, in which the lubricating composition further comprises at least one antioxidant additive, in particular selected from diphenylamine, phenols, phenol esters and mixtures thereof.

6. Use according to the preceding claim, wherein the lubricant composition comprises from 0.05% to 2% by weight, preferably from 0.5% to 1% by weight, of antioxidant additive, relative to the total weight of the composition.

7. Use according to any one of the preceding claims, in which the lubricating composition further comprises at least one detergent additive distinct from the boron derivative as defined according to any one of claims 1 or 2, chosen from metal salts. alkaline earth metal, preferably from calcium salts, magnesium salts and mixtures thereof.

8. Use according to any one of the preceding claims, in which the lubricating composition comprises at least one additive improving the viscosity index chosen from homopolymers or copolymers, hydrogenated or non-hydrogenated, styrene, butadiene and l. isoprene, preferably which is a hydrogenated styrene / isoprene copolymer.

9. Use according to the preceding claim, in which the composition comprises from 2% to 15% by weight of additive improving the viscosity index, relative to the total weight of the composition.

10. Use of at least one boron derivative, in particular as defined according to claim 2, in a lubricant composition comprising at least one base oil, the boron content in the composition being between 150 ppm and 350 ppm in weight, to prevent and / or reduce pre-ignition, in particular at low speed, in a vehicle engine, preferably a motor vehicle, said lubricating composition being used during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without adding new lubricating composition.

11. Use of at least one boron derivative, in particular as defined according to claim 2, in a lubricating composition comprising at least one base oil, the boron content in the composition being between 150 ppm and 350 ppm in weight, to limit the degradation of the performance of prevention and / or reduction of preignition, in particular at low speed, in a vehicle engine, preferably of a motor vehicle, of said composition, after its implementation during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without adding new lubricating composition.

12. Use of at least one boron derivative, in particular as defined in claim 2, in order to increase the ignition temperature, measured by high pressure differential scanning calorimetry, of a lubricating composition, in particular. at least 2%, preferably at least 4%, said composition being used during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without addition of new lubricating composition, compared to a used lubricating composition free of any compound derived from boron, the boron content in the composition being between 150 ppm and 350 ppm by weight.

13. Method for preventing and / or reducing pre-ignition, in particular at low speed, in a vehicle engine, preferably of a motor vehicle, comprising at least the following steps:

a) bringing the engine into contact with a lubricating composition comprising at least one base oil and at least one boron derivative, the boron content in the composition being between 150 ppm and 350 ppm by weight;

14. The method of the preceding claim, wherein the lubricating composition is as defined in any one of claims 2 to 9.

15. Use of a lubricating composition comprising:

(i) at least one boron derivative, the boron content in the composition being between

150 ppm and 350 ppm by weight; and

(ii) at least one base oil,

said composition having undergone an iron-catalyzed oxidation at a temperature above 150 ° C, preferably between 150 ° C and 170 ° C and for a period of at least 110 h, preferably between 120 h and 150 h, according to the GFC Lu-43A-11 method.